The present invention relates to spray nozzles and, more particularly to a spray nozzle, such as for use in container coating applications, which produces an improved asymmetrical distribution of the fluid discharge.
In order to protect substances such as food and beverages from contamination, a coating is typically applied to the inside surfaces of containers in which such substances are stored. This coating prevents the contents of the container from coming into direct contact with the bare metal or plastic interior surfaces of the container. With standard cylindrical containers or cans, this coating is generally applied to the interior of the container before the top is affixed through the use of a spray nozzle which is arranged to discharge through the open end of the container. As the coating is being discharged from the nozzle, the container is rotated about its longitudinal axis so as to ensure that all of the interior surfaces are coated.
The coating material used on the inside surfaces of the containers represents one of the most significant costs associated with a container manufacturing operation. Accordingly, in order to minimize consumption of the coating material, it is desirable to utilize a spray nozzle which produces a tightly controlled spray pattern which applies a thin, even coating on the interior surfaces of the container while minimizing the amount of spray that does not contact the interior of the container. Additionally, since the containers can have a wide variety of sizes it is also desirable that the spray nozzles be easily customized to provide a tightly controlled pattern for a particular container configuration.
To help achieve an even coating, the coating material is generally applied using spray nozzles that are configured to produce an asymmetrical distribution of the fluid discharge. These nozzles are arranged at an angle relative to the longitudinal axis of the container so that the heaviest portion of the discharge is directed towards the far, closed end of the container. Thus, the asymmetrical distribution helps compensate for the greater distance the coating material must travel to reach the closed end of the container and, in turn, the greater surface area of the interior of the container that this portion of the discharge pattern must cover.
One common method by which to measure the distribution of the fluid discharge of a particular nozzle is to discharge the nozzle onto what is referred to as a distribution table. The distribution table has on its upper surface a plurality of evenly spaced troughs that have relatively sharp edges which divide the spray into segments and then channel the liquid sprayed into them into test tubes or graduated cylinders for measurement. The spray nozzle is generally oriented relative to the distribution table so that the spray nozzle points downward towards the table with the centerline of the orifice being perpendicular to the surface of the table. The nozzle is centered on one trough and is located at some predetermined distance above the table. For nozzles which produce a flat, fan type spray pattern, including those typically used in container coating applications, the nozzle is arranged so that the widest portion of the fan extends perpendicularly relative to the troughs.
With the asymmetrical pattern spray nozzles presently used in container coating applications, it has been difficult to achieve a thin, even coating on the interior of the containers which avoids waste of the coating material. For example, one type of nozzle which can produce an asymmetrical spray pattern is what is referred to as a drumhead nozzle. A drumhead type nozzle has a discharge orifice configured to produce a fan-shaped discharge pattern with a maximum amount of fluid being discharged at one end of the fan and with the amount of fluid decreasing linearly to a minimum amount at the other end of the fan. With this type of distribution pattern, however, drumhead type nozzles cannot produce a thin, even coating along the bottom of the container and at the intersection between the bottom and the cylindrical side wall of the container. Accordingly, to ensure that all of these surfaces are adequately coated, extra coating material must be applied and, as a result, deposits of excess coating material form in some areas.
Another spray nozzle configuration which can be used in container coating applications is described in U.S. Pat. Nos. 3,697,313 and 3,737,108. In contrast to the drumhead type nozzle which has the maximum discharge at or closely adjacent one end of the spray fan, this type of nozzle produces a discharge pattern where the heaviest discharge or flow of fluid is produced at a point approximately midway between the middle and one end of the total fan-shaped pattern produced by the nozzle. With this type of nozzle, the level or amount of discharge tapers linearly from the location of maximum discharge to either end of the spray pattern. The discharge orifice in the nozzle is produced by making two separate cuts in a dome-shaped end of a cylindrical blank nozzle body using sharply pointed rotary cutting wheels. The resulting orifice has sharply pointed ends and expands to a maximum opening that is arranged asymmetrically between the sharply pointed ends of the orifice.
However, like the drumhead type nozzles, this type of nozzle cannot apply a thin, even coat on the all of the interior surfaces of the container resulting in inefficient consumption of the coating material, which, in turn, results in increased manufacturing costs for the containers.
Accordingly, in view of the foregoing, it is a general object of the present invention to provide a spray nozzle, such as for use in container coating applications, which produces an improved asymmetrical distribution of the fluid discharge.
A more specific object of the present invention is to provide a spray nozzle for use in container coating applications which produces a tightly controlled fluid discharge pattern so as to be able to apply a thin, even coat on the interior surfaces of a container thereby optimizing consumption of the coating material.
A related object of the present invention is to provide a spray nozzle as characterized above which can be easily customized for use with containers having different configurations.